Shuttle-type printers are a class of printers having a movable shuttle or carriage that traverses back and forth across a printing surface. A printhead is mounted on the carriage and synchronized with carriage movement to print desired images. The shuttle class of printers includes both impact printers, such as dot matrix and daisy-wheel printers, and non-impact printers, such as ink-jet printers.
Conventional shuttle-type printers have a media feed assembly which advances a recording media through the printer and a separate shuttle drive assembly which maneuvers the carriage over the recording media. The media feed assembly typically consists of friction rollers or a tractor feed mechanism and a motor coupled to rotate them. The shuttle drive assembly typically consists of a motor and a belt and pulley assembly which connects the carriage to the motor. Common motors used in these assemblies include DC motors which change speed and direction in relation to the level and polarity of DC voltage applied thereto, and stepper motors which change speed and direction in response to intermittent pulses.
The two motors used for the media feed and shuttle drive assemblies are controlled in a synchronized manner. The carriage motor drives the carriage back and forth over the media in periodic swaths. At the end of each swath, the media feed motor increments the recording media within the printer to the next line. Special control circuitry is employed to synchronize the operation of these two motors.
A problem of prior shuttle-type printers concerns the complexity of controlling the independent operation of the media feed motor and the carriage motor. Sophisticated hardware and firmware are necessary to manage both motors. In addition to the cost of each motor, there are extra costs resulting from multiple connectors, logic boards, and cables needed to operate both motors, as well as added power supply requirements.
This invention overcomes the above problem by providing a mechanism for simultaneously moving the carriage and indexing the media by using a single motor. The mechanism thereby eliminates one motor and its associated logic board, connector, cable, and power supply overhead.